Carburetor by-pass control



Feb. 8, 1955 R. J. BRUNNER CARBURETOR BY-PAss coNTRL Filed March 5, 1947 mw /4 \m%\m www /,Mmlmw w@ Qly M i@ m JQ Q www @u wM/NM A BY Pff, m/lf/ United States Patent() CARBURETOR BY-PASS CONTROL Richard J. Brunner, Detroit, Mich., assignor to Bendix Aviation Corporation, South Bend, Ind., a corporation of Delaware Application March 5, 1947, Serial No. 732,546

4 Claims. (Cl. 261-41) The present invention relates to carburetors for internal combustion engines and more particularly to a control system in noat type carburetors for varying the idling fuel-air mixture in accordance with engine requirements.

Une ot' the principal objects of the present invention is to provide a carburetor for an internal combustion engine wherein the proper fuel-air mixture is supplied the engine while said engine is idling under varying operating conditions.

Another object of the present invention is to provide a carburetor for the aforesaid engine, wherein the fuel-air mixture for idling is automatically adjusted in response to variations in intake manifold pressure.

Another object of the invention is to provide in an internal combustion engine carburetor, a pressure responsive mechanism for leaning the fuel-air mixture during idling when the intake manifold vacuum becomes abnormally low, such as would occur when the engine is placed under load during idling.

Still another object of the invention is to provide in a carburetor a simple and easily assembled mechanism for varying the quantity of fuel and air in the fuel-air mixture during idling of the engine.

The present invention is primarily concerned with a means for providing the proper fuel-air mixture under varying engine idling conditions by regulating the pressure above the fuel in the fuel bowl in response to changes in intake manifold vacuum. The mechanism for accomplishing the aforementioned objectives consists of a conduit connecting the fuel bowl above the fuel with the induction passage on the engine side of the throttle valve and a valvular means in said conduit adapted to close and open the conduit as the manifold vacuum rises above or falls below a predetermined value. For normal idling operation, the valve in the conduit connecting the fuel bowl with the induction passage remains closed and normal atmospheric or air entrance pressure is maintained in the fuel bowl above the fuel. As engine speed decreases during idling and the manifold vacuum falls to a subnormal value, the valve controlling the conduit opens and permits engine suction to be transmitted to the fuel bowl, thus causing depression of the air pressure above the fuel and consequently a decrease in the fuel delivered by the idling system, as well as providing through said conduit an additional supply of air for said engine. The leaner fuel-air mixture obtained by the decrease in fuel supply and the increase in air supply satisfies the requirements of the engine idling under the aforementioned subnormal speed and manifold vacuum. When the engine speed and intake manifold vacuum return to normal, the valvular means again closes the conduit to provide the normal idling fuel-air mixture.

The present invention may be clearly understood by referring to the accompanying drawings, wherein:

Figure 1 is a vertical cross-sectional View of a car'- buretor for an internal combustion engine in which certain elements of the carburetor have been rearranged to more clearly illustrate the present invention; and

Figure 2 is a fragmentary cross-sectional view of the carburetor shown in Figure 1 in which the operation of the present invention is further illustrated.

The `embodiment of the invention illustrated in the accompanying drawings is shown in combination with a conventional updraft carburetor generally comprising a throttle body 10, a float chamber 12 and an airintake 14 having therein a choke valve 16, a main discharge system generally shown at 18 and the lower section of an idle ice system generally shown at 20. The. throttle body 10 contains the upper section of the idling system and auxiliary idle control 22 together with a conventional throttle valve 24 and venturi tube 26. The induction passage of the carburetor extends through air intake 14 and throttle body 10 and is controlled at the air inlet by choke valve 16 mounted on shaft 26 and at the mixture outlet end by throttle valve 24 mounted on shaft 30 which is manually actuated through a throttle valve lever and linkage (not shown) mount'ed on one end of said shaft. The venturi tube 26 is mounted in throttle body 12 adjacent the air intake and held in place by an annular rib 32 being clamped in annular recess 34 in the end of said air intake 14.

The main fuel discharge jet 18 extends from near the bottom or' the carburetor adjacent the fuel bowl to the throat of the venturi and includes a main discharge tube 36 having annular recesses 36 and 40 which together with the bore for the discharge jet form annular tuel or fuel and air passages 42 and 44 around the main discharge tube. These two passages are connected with the interior of said tube by a plurality of ports 45 and 46 spaced longitudinally along said main tube. Passage 44 communicates with the idling system 20 through duct 47, and passage 42 is connected by conduit 48 with the space behind the venturi tube 26, said space being vented to the induction passage through port 49. The main fuel metering orifice 5U is disposed in main fuel conduit 5l and is connected with the Iuel bowl by a conduit 52. The fuel supply to the carburetor is controlled by a needle valve,

54- slidably received in a sleeve 55 and a float 56 supported by an arm 58 which is pivoted on a pin 59 securedto bracket 60, said arm being adapted to engage the.

lower end of said needle valve and to regulate said valve in accordance with the quantity of fuel being withdrawn from the fuel bowl. The fuel bowl above the fuel level is vented to the air inlet of intake 14 by conduit 61 so that the pressure above the fuel may be maintained at substantially atmosphericV pressure during normal engine. Said conduit is provided with a replaceableoperation. restriction 62 which may be used in adjusting air flow through said conduit and consequently the pressure above (only one end of said valve being shown in the drawings) y for controlling the quantity of air permitted to bleed into the upper end of conduit 63 on the posterior side of jet 66 and to form therein an emulsion with the idling fuel.7

The fuel and air emulsion formed at the upper portion of conduit 63 by the air entering said conduit through duct- 68 is further emulsified before being discharged vthrough port 64 by air entering port 65 when the throttle valve is When the.

in closed or substantially closed position. throttle valve is opened, the flow of air into port 65 is interrupted so that only the original fuel-air emulsion is discharged into the induction passage by the idling system.

When the engine speed and manifold vacuum become subnormal during idling as a result of increased load, the

fuel-air mixture tends to become excessively rich and a heavy smoke 1s given olf in the engine exhaust'. In order to lean the mixture for the slower idling speeds so that' said mixture will more nearly satisfy engine requirements, an auxiliary idle control mechanism 22 has been included in the carburetor. This mechanism broadly consists of a passageway connecting the fuel bowl above the fuel with the induction passage on the engine side of the throttle valve together with a pressure responsive valve for opening the passageway when the manifold vacuum falls below a certain predetermined value. The mechanism includes a cylinder 72, a port 74 connecting the central portion of said cylinder with the fuel bowl, and a conduit 76 having a restriction 78 therein connecting the upper portion of said cylinder with the induction passage posterior to the throttle valve; A reciprocable hollow piston '80 is disposed in said cylinder and is urged to its lowerrnost position by a calibrated coil spring 82 which reacts between the upper end of cylinder 72and the internal bottom of said piston. The piston is provided with an annular recess 83 aboutthe central portion thereof which registerswitlrportlv 74'when the piston is in the lower end of cylinder7'2`; The'annular recess communicates with the hollow'interior of'piston S'througlr one or more calibrated'orilices 84 in the central portion of said recess. When'pistonSl) is inthe lower end of cylinder 72, as shownn in..Figure `l,` theoat chamber above the fuel level communicateswith-the induction passage on the engine sideof` the throttlevalve through portv 74, annular recess Sr-port 84',V interior-of piston 80, cylinder 72 andl conduit 76grandby thereffect of enginefsuction transmitted through said passagewayythepressure above the'fuel is decreased to'a value appreciably below atmospheric pressure. Duringnormal engine idling operation, piston 80 is drawn into tlreupperfend of cylinder 7-2, andthe lower end of annular recess83 isfmovedto a position entirely above port '74-1so-that'the owof air from the oat chamber throughsaidf'passageway is interrupted until the intake manifoldivacuum'againfallsbelow a predetermined value andpiston 80^has returned to the lower endof cylinder 72. Thelower-'end of-cylind'er 72"below piston 80 is vented' to theatmosphere throughk duct'86' and conduit 61 to permit free movement ofv the piston in said cylinder duringroperation of the engine.

yWhiletherpassageway'is open, air flows through conduitA 61, `restriction v62' into the space above the fuel and our'through the passageway to the induction passage. By correlating'the effective size of restrictions 62, 78 and 84'andi`the calibration of spring 82, a range of pressure depression above-the fuel, as well as the time when the piston willopen and close the passageway, can be predetermined; The spring and restrictions are preferably so Ycalibrated Athat the passageway will open when the vacuum inthe intake'manifold falls below about eighteen inchespf mercury.

ln; the 'operation of'the carburetor described herein, with the engine' running at part or wide open throttle, fuel is delivered lfrom the fuel-bowlY through conduit 52, main metering.` jet 50', conduit 51 and main discharge jet 1'8, andpt-hence discharged into'the induction passage in the throat of: venturif26. As fuelfiows through the discharge iet, 'air isfbledinto-the` fuel stream through ports 45 from annularpassage42andconduit 48 connecting said passage with the space behind venturi 26. Under certain conditi'crnsrdurin'g'normal4 part and wide open throttle, air is also bled"'into Vthe'fuel stream in themain discharge jet frorrrA annular passage 44', the air being supplied by backflow in theidling system. lt is sometimes found desirable totinclude'archeckrvalve in the idling system to prevent any appreciableamount of backflow through the idling system, thoughsuch anarrangement has not been included in the presentv embodiment: As the throttle valve approaches closed-position, engine suction lowers the pressure in the idlingsystern and-causesthe fuel to flow through the ports iti-"andthe annular passage 44' and thence through the idlingsystem into the yinduction passage adjacent the throttle' valve; As'the fuel flows upwardly through condnit=-63z itpasses through idling metering iet 66 and thereafter mieswi'th the air bled into the idling system through duct 68.'forming an 'emulsion which aids in complete atnmization oftbe fuel as it is discharged through port 64 into theinduction passage. Ports 64 and 65 are so arranged adacent the throttle valve that when said valve is closed. portv 64 is nnsterior to said valve and port 65 iS-pmfm-imthereto. With this relationship. air is bled into port-6 when the throttle valve is in closed or substantially closedlnosition. thus providing air to further emnlsifv the idlne fuel as wellas'prfviding'additonal air for the cornbnefihnf nf`saidf fuel. When the throttle valve has been onenedtn a-'nnintwhere port'iisv entirelv on the engine side ofi-wifiv valve. onlvthe oronal emulsion formed in conduit.- S3-passesA through port 641 or through. both ports 64iandf65.

tWhile the engine is idling normally, the manifold vacuum. isfgenerally maintained above about eighteen inches of mercury. and wththis vacuumfpiston 8i]y is difawn'finto andlheld.l in: the upper end'nf' cylinder '72; as shown inilfiguie;2;y in oppositionto the force4 of spring 82 urgingrsaidipiston:toward'thei lower end ofasaid cylinder.

With the piston in the upper end of cylinder 'the-annu.-

lar recess 83 and port 84 are not in communication withport 74 leading to the fuel bowl; the pressure above the fuel in said bowl, therefore,premains at substantially atmospheric pressure as transmitted through conduit 61 from the entrance of air intake 14.

As the speed of the engine isv decreased while the engine is idling, such as would occur if the engine were placed under load, the manifold vacuum decreasesappreciably, and as a result the idling fuel-air mixture becomes excessively rich fortheslower idling speed; When the manifold vacuum `decreases to` a predetermined. value, spr-ing S2 forces piston 80 to its lowerrnost position. in cylinder 72. The recess 83 and port 84 now register With port 74, and the fuel-bowl and induction passageA are indirect communication with one another through port 74, recess 83, port 84, cylinder 72 and/conduit 7'6. The engine suction transmitted through the foregoing passageway to the space above the fuel in the fuel bowl causesasubstantial lowering ofthe pressure therein and consequently ade.- crease i`n thequantity delivered' to the idlin'gsystemjfiiom the fuelbowl. to theA idling 'system While -the pistonA is in the position shown in Figure l, together withl the airow throughthe passagewaleansthe fuel-air mixture suthciently to satisfy enginerequirements fory the slow'idling speed. `Whenthe load is removed while the engine is still idling, the mani:

fold vacuum increases sutciently to liftpiston '8G/'to its" uppermost' position in cylinder` 72 thus closing the passageway between'the'fuel bowl'an'dthe induction passage.

Whilein the drawings only'the mainfueldischarge and' idling systems together with the present idling control' mechanism are shown, it is understood that other fuel systemsnormally present in conventional carburetors for internal combustion engines, such as the economizingand accelerating'systems, are preferably included in the carburetor in which the present invention is used;

It is contemplated that other arrangements of elements comprising the'presentinvention than those shown in the accompan-yingdrawings maybe provided` without departingfrom the'scope-of the'present inventionyfor example.

piston 80 may be providedf withy a multiplicity ofannular recesses 83 andportsS-l so arranged'A that they willregisterv successively with-portV 74 as piston 80 descends in cylinder' 72, and gradually increase the` effective size of` the passageway as .the intake manifold vacuum decreases. Although this modification'has not been described in' detail herein or illustratedin'the accompanying drawings,l the changesnecessaryto construct this modication of :my

invention will be apparent tothose skilled in the art.'

I claim: 1. In'an'engine carburetor having an induction passage With a throttle-valve-therein: a, fuel bowl, a vent of limited" necting'the bowl above the fuelwith the induction passage. on the engine side of the throttle, a sliding valve meansin.

saidpassagewayurged upwardly by manifold vacuumin said induction passage, a recess in said valve, means adapted to provide communication between saidbowl'and said induction passage when said valve means is in its means downwardly in opposition to manifold vacuum.

2. ln an internal'combustion engine carburetor havingA an induction passage with a throttle valve therein: a fuel bowl: an idling system communicating at one end with said fuel bowl' and at the other end with the induction passage on the engine side of said throttle valve: acvlinder: a conduit connecting the upper end of said cylinder with the induction passage on the engine side of said throttle valve: a port' in the side of said cylinder connecting said cylinder with the space above the fuel in said fuel bowl; a cup-shapedpiston insaid cylinder having its open end at the ton; an annular recessin said piston; a port connecting said recess with the interior of saidcupshapedvpiston; and a spring adapted to urgesaidpiston-to its lowerrnost position-intopposition tomanifold vacuum, the recess and port in saidzpistonbeing adaptedv'to register withl the port in. said cylinder. when the "cylinder is.v nits lowerrnost position. v

3. In; an internalcombustion engine carburetorhaying an: induction.passageI with Va. throttle valve thereint at-fuel The diminished quantity off'fuel suppliedi bowl; a vent of limited ow capacity for said fuel bowl; a main discharge jet adapted to supply fuel from the fuel bowl to said induction passage; an idling system having a conduit communicating at one end with said discharge iet and at the other end with the induction passage on the engine side of said throttle valve; a cylinder; a conduit connecting the upper end of said cylinder with the induction passage on the engine side of said throttle valve; a port connecting a central portion of said cylinder with the space above the fuel in said fuel bowl; a cup-shaped piston in said cylinder having its open end at the top; an annular recess in said piston about the central portion thereof; a port connecting said recess with the interior of said cup-shaped piston; and a spring adapted to react between said piston and the upper end of said cylinder for urging said piston to its lowermost position in opposition to intake manifold vacuum, the port in said piston and the port in said cylinder being in communication with one another when said piston is in its lowermost position, whereby manifold vacuum is transmitted to the fuel bowl above the fuel to vproduce a leaning effect on the fuel-air mixture for slow idling.

4. In an internal combustion engine carburetor having an induction passage with a throttle valve therein: a fuel bowl, an idling system communicating at one end with said fuel bowl and at the other end with the induction passage on the engine side of said throttle valve, a cylinder, a conduit connecting the upper end of said cylinder with the induction passage on the engine side of said References Cited in the tile of this patent UNITED STATES PATENTS 1,948,135 Sands Feb. 20, 1934 20 1,958,690 Ball et al May l5, 1934 2,029,142 Wemhoner Jan. 28, 1936 2,229,851 Hutord Ian. 28, 1941 

